1. Field
The present disclosure relates to an anode for a lithium secondary battery and a lithium secondary battery including the same, and more particularly, to an anode for a lithium secondary battery having an improved initial efficiency, an increased reversible capacity, and improved lifetime characteristics, and a lithium secondary battery including the same.
2. Description of the Related Art
In general, lithium has been used as an anode active material in lithium secondary batteries. However, since a short circuit in a battery may occur due to the formation of dendrites when lithium is used, there may be a danger of an explosion, and thus, a carbon material is widely used as an anode active material instead of lithium.
Crystalline carbon, such as graphite and artificial graphite, and amorphous carbon, such as soft carbon and hard carbon, may be used as a carbon active material. The amorphous carbon may have high capacity, but irreversibility during charge and discharge processes may be high. Graphite is used as a representative of the crystalline carbon, and has been used as an anode active material because graphite has a high theoretical specific capacity of about 372 milliampere-hours per gram (mAh/g). However, even when a theoretical capacity of the graphite or the carbon active material may be relatively high, the theoretical capacity thereof is only about 380 mAh/g, and thus, the foregoing anode active material may not have sufficient capacity for the development of a higher-capacity lithium secondary battery.
In order to overcome such limitations, a metal or intermetallic compound anode active material is being actively studied. For example, lithium secondary batteries using a metal or a semimetal, such as aluminum, germanium, silicon, tin, zinc, and lead, as an anode active material have been studied. These materials may have high energy density as well as high capacity, and may store and release a greater amount of lithium ions than the anode active material using a carbon material, and thus, these materials may be considered as a material for a battery having improved capacity and energy density. For example, it is known that pure silicon has a theoretical capacity of about 4,017 mAh/g.
However, since these materials have shorter cycle life than the carbon material, the short cycle life may be an obstacle to the commercialization thereof. The reason for the short cycle life is that, in the case where inorganic particles, such as silicon or tin particles, themselves as an anode active material are used as a lithium storing and releasing material, the conductivity between active material particles may decrease due to volume changes during charge and discharge processes, or delamination of an anode active material from an anode current collector may occur.
In particular, in the case where an active material has a small particle diameter or a large specific surface area, a surface for contacting an electrolyte may be larger, and thus, a side reaction with the electrolyte during initial intercalation of lithium may increase. As a result, an initial irreversible capacity may be increased and thus, an initial efficiency may be decreased.
Thus there remains a need for improved anode materials.